Method and system for controlling a flying wing

Abstract

The invention relates to a method for control of a flying wing. The flying wing is arranged to be controlled to move along a predetermined trajectory by means of a fluid stream passing a wing of the flying wing. The flying wing comprises at least one control surface for controlling the movement of the flying wing along the predetermined trajectory. The flying wing is positioned in a reference frame where the x-axis is directed horizontally along a level L above which the flying wing moves, the y-axis is perpendicular to the x-axis in a vertical direction and the z-axis is perpendicular to the x-axis along the level L in a direction along the principal direction of the fluid stream. The invention further relates to a system comprising a flying wing and a computer-readable medium for use with a flying wing.

The invention claimed is: 
     
       1. A method for control of a flying wing, the flying wing being arranged to be controlled to move along a predetermined trajectory by means of a fluid stream passing the flying wing; the flying wing comprising a wing and at least one control surface for controlling a movement of the flying wing along the predetermined trajectory, the flying wing being positioned in a reference system where the x-axis is directed horizontally along a level L above which the flying wing moves, the y-axis is perpendicular to the x-axis in a vertical direction and the z-axis is perpendicular to the x-axis along the level L in a direction along the principal direction of the fluid stream, the flying wing being arranged to be attached to said level L by means of a tether attached to a structure positioned at said level L, wherein the control of the flying wing is arranged to be performed using a horizontal position of the flying wing, a vertical position of the flying wing, a heading of the flying wing and a yaw rate of the flying wing, where the horizontal position, the vertical position, the heading and the yaw rate can be measured or modelled, wherein the method uses as measured input values the heading, pressure to obtain measured vertical position, yaw rate and speed of the flying wing, wherein the method comprises:
 controlling the movement of the flying wing along the predetermined trajectory during a sensor feedback phase using measured values of heading, vertical position and yaw rate and modelled values of horizontal position, 
 switching between said sensor feedback phase and a model feedback phase after a predetermined distance along the predetermined trajectory has been traversed and when a deviation between the measured value of the vertical position and a modelled value of the vertical position is below a threshold value, and 
 controlling the movement of the flying wing along the predetermined trajectory during said model feedback phase using modelled values of heading, vertical position, horizontal position and yaw rate. 
 
     
     
       2. The method of  claim 1 , wherein the sensor feedback phase of the method comprises:
 continuously updating the heading by integrating the measured yaw rate, 
 iteratively adapting the heading based on the measured vertical position after a predetermined distance along the predetermined trajectory has been traversed, 
 iteratively adapting the yaw rate based on the measured vertical position after a predetermined distance along the predetermined trajectory has been traversed, 
 calculating a modelled adaptation of the yaw rate in order to prepare for the transition between the sensor feedback phase and the model feedback phase, 
 calculating the flying wing's modelled horizontal position and modelled vertical position by dead reckoning using the measured speed and measured heading of the flying wing, 
 iteratively adapting the modelled horizontal position of the flying wing based on the average speed of a first part of the predetermined trajectory and the average speed of a second part of the predetermined trajectory, 
 iteratively adapting a horizontal drift speed based on the average speed of a first part of the predetermined trajectory and the average speed of a second part of the predetermined trajectory, 
 iteratively adapting the modelled vertical position based on the difference between the modelled vertical position and the measured vertical position, and 
 iteratively adapting a vertical drift speed based on the difference between the modelled vertical position and the measured vertical position. 
 
     
     
       3. The method of  claim 1 , wherein the model feedback phase of the method comprises:
 continuously calculating the modelled heading by integrating the modelled yaw rate, 
 iteratively adapting the modelled heading based on the difference between the measured vertical average position and the modelled vertical average position after a predetermined distance along the predetermined trajectory has been traversed, 
 iteratively adapting the modelled yaw rate based on the difference between the measured vertical position and the modelled vertical position after a predetermined distance along the predetermined trajectory has been traversed, 
 calculating the flying wing's modelled horizontal position and modelled vertical position by dead reckoning using the measured speed and measured heading of the flying wing, 
 iteratively adapting the modelled horizontal position of the flying wing based on the average speed of a first part of the predetermined trajectory and the average speed of a second part of the predetermined trajectory, 
 iteratively adapting a horizontal drift speed based on the average speed of a first part of the predetermined trajectory and the average speed of a second part of the predetermined trajectory, 
 iteratively adapting the modelled vertical position based on the difference between the modelled vertical position and the measured vertical position, and 
 
       iteratively adapting a vertical drift speed based on the difference between the modelled vertical position and the measured vertical position. 
     
     
       4. The method of  claim 1 , wherein the vertical position and the horizontal position are Cartesian positions or the vertical position and the horizontal position are a vertical angle and a horizontal angle respectively. 
     
     
       5. The method of  claim 1 , wherein the heading is obtained from a heading sensor, the pressure is obtained from a pressure sensor, the yaw rate is obtained from a yaw rate sensor and the speed is obtained from a speed sensor. 
     
     
       6. The method of  claim 1 , wherein the flying wing comprises a turbine for generating electrical energy by the movement of the flying wing through fluid of the fluid stream and where the flying wing is submerged in the fluid. 
     
     
       7. A system comprising:
 a flying wing comprising a wing and at least one control surface for controlling the movement of the flying wing along a predetermined trajectory, the flying wing being arranged to move along the predetermined trajectory by means of a fluid stream passing the wing, the flying wing being positioned in a reference system where the x-axis is directed horizontally along a level L above which the flying wing moves, the y-axis is perpendicular to the x-axis in a vertical direction and the z-axis is perpendicular to the x-axis along the level L in a direction along the principal direction of the fluid stream, 
 wherein the system uses measured values of yaw rate, heading and vertical position and a modelled value of horizontal position during a sensor feedback phase of movement along the predetermined trajectory, and modelled values of yaw rate, vertical position, horizontal position and heading during a model feedback phase of movement along the predetermined trajectory for control of the flying wing, 
 wherein the system uses as measured input values the heading, pressure to obtain measured vertical position, yaw rate and speed of the flying wing during the sensor feedback phase, and 
 wherein said sensor feedback phase is switched to the model feedback phase after a predetermined distance along the predetermined trajectory has been traversed and when a deviation between the measured value of the vertical position and the modelled value of the vertical position is below a threshold value. 
 
     
     
       8. The system of  claim 7 , wherein the system further comprises a level pressure sensor located at the level L above which the flying wing moves for measuring the level pressure at said level L, the level pressure being used to improve the calculation of the vertical position of the flying wing over the level L to which it is attached. 
     
     
       9. The system of  claim 7 , wherein the flying wing is arranged to be attached to said level L by means of a tether attached to a structure positioned at said level L. 
     
     
       10. The system of  claim 7 , wherein the heading is obtained from a heading sensor, the pressure is obtained from a pressure sensor, the yaw rate is obtained from a yaw rate sensor and the speed is obtained from a speed sensor. 
     
     
       11. The system of  claim 10 , wherein the heading sensor is an accelerometer, the yaw rate sensor is a gyroscope, the pressure sensor measures a wing fluid pressure at a surface of the flying wing and the speed sensor is one of a turbine configured to provide information on revolution rate thereof, an electric current meter or a pressure based meter. 
     
     
       12. The system of  claim 7 , wherein the flying wing comprises a turbine for generating electrical energy by the movement of the flying wing through fluid of the fluid stream and where the flying wing is submerged in the fluid. 
     
     
       13. A non-transitory computer-readable medium for use with a flying wing having, said computer-readable medium having computer executable instructions stored therein for performing the method of  claim 1 .